package hDOJ;

import java.util.Scanner;

public class Main01 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()) {
            int score = sc.nextInt();
            if((90 <= score)&&(score <= 100)) {
                System.out.println("A");
            }else if((80 <= score)&&(score <= 89)) {
                System.out.println("B");
            }else if((70 <= score)&&(score <= 79)) {
                System.out.println("C");
            }else if((60 <= score)&&(score <= 69)) {
                System.out.println("D");
            }else if((0 <= score)&&(score <= 59)) {
                System.out.println("E");
            }else {
                System.out.println("Score is error!");
            }
        }
    }
}
